Add guidance about SDMs to User Guide

[kandersolar]

• I am familiar with the contributing guidelines
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels (including remote-data) and Milestone are assigned to the Pull Request and linked Issue.

Continuing in a broader thrust of developing our user guide section. Previously:

• Create weather data/iotools page in User's Guide #1754
• Add spectral mismatch model comparison table #2353

[markcampanelli]

In terms of "Guaranteed convergence", I would caution here that lambertw-based solvers can suffer from numerical issues in some regimes. IIRC, this was a main issue that Ken Roberts tried to solve in https://arxiv.org/abs/1504.01964. (A second would be a method that converges faster than lambertw.) See also #1856. Speaking of which, would you be interested in any help getting the LogWright based solvers across the finish line @kandersolar? Review, testing, inter-comparisons, ...?

[markcampanelli]

Also, the use of "explicit" here is subject to debate, as I wouldn't be surprised if there is an iterative solver hiding underneath scipy's implementation.

[cwhanse]

I'm fairly sure scipy uses Halley's method under the hood. The point about "explicit" is that the solution of the diode equation is explicit, not that calculation of its value doesn't require an iterative method. Maybe that distinction is unclear in the table headings.

Ken's paper is about avoiding numerical overflow at very large arguments, which can occur in the "v_from_i" calculation. pvlib handles those in a manner similar to Ken's, by solving for log(W(x)) rather than W(x).